A magnetic disk, which is a recording medium for a hard disk device (HDD), is made of a circular plate, such as aluminium and glass serving, as a base, and is configured to coat a magnetic film on its surface and further to coat a protective film thereon. The surface of this protective film is preferably a smooth flat surface with the least unevenness, such as a projection, and is required to have a good recording performance for the magnetic film. Conventionally, the smoothness of the protective film is inspected by a gliding inspection device and the recording performance of the magnetic film is inspected by a certification inspection. An apparatus disclosed in JP H6-162496 is known as an inspection apparatus of a magnetic disk capable of efficiently performing gliding inspection and certification inspection.
The apparatus disclosed in JP H6-162496 includes two head moving mechanisms, wherein any heads to perform the burnishing or the gliding inspection and a head to perform the certification inspection are arranged perpendicularly to a head moving direction, and the movement of each head for head switching is not performed at the head moving mechanism side but is performed by moving the spindle side perpendicularly to the head moving direction.
The apparatus disclosed in JP H6-162496 can perform the moving mechanism for switching the head with a single spindle moving mechanism so that the mechanism part can be simplified and high accuracy head positioning can be achieved. In addition, it is not necessary to move the heads for switching the heads for the gliding inspection and the certification inspection so that horizontal blurring can be prevented and high speed and high accuracy inspection can be performed for the magnetic disk.
The gliding inspection uses a gliding head, which is assembled with a piezo vibration sensor and performs the inspection by detecting the vibration occurred at the head when a projection on the disk is touched. Relying on the fact that a flying height of the head depends on a revolving speed of the disk, the height of the projection to be detected is set by controlling the revolving speed of the disk. On the other hand, the certification inspection uses a head with recording and replaying capabilities and inspects by recording inspection signals on the disk during rotation at the predetermined revolving speed and replaying the recorded inspection signal.
Accordingly, these two inspections cannot be performed at the same time because they have different conditions for the revolving speed. Therefore, with the present circumstances, the certification inspection is performed after the gliding inspection is performed on a single inspection spindle or the inspections are performed at the same time respectively on different spindles.